Investigations of gas-phase lithium-peptide adducts: Tandem. mass spectrometry and semiempirical studies

Tandem mass spectrometry using a hybrid mass spectrometer of BEqQ geometry was used to investigate the gas-phase formation of the [An (+) Li - H)(+) ion from lithium-peptide adducts. High resolution mass measurements as well as precursor and product ion scans of five peptides indicate that one source of [An (+) Li - H) arises from [An (+) Li](+). Semiempirical calculations (MNOO) and metastable ion decomposition studies of the peptide Gly-Gly-Gly show that the lithium ion prefers to coordinate to the three internal carbonyls of the neutral molecule to give a species that is energetically more stable than the lithiated zwitterion by 305 kJ/mol. Theoretical and experimental evidence suggest that the monolithiated precursor ion population may be a distribution of structural isomers. (J Am Soc Mass Spectrom 1990, 1, 473-480).

Direct modeling of the output parameters of an optical recording

The relationship between the recorded bit size and write beam characteristics has been analyzed and calculated. A unified formulation for the reflectivity after recording is introduced, and a new analytical description of reflection contrast is established. The effects of read/write beam characteristics on the recording contrast are discussed. The theoretical analysis results are well supported by experiment results.

[Dynamic changes of lactate and pyruvate concentrations in human uterine fluid]

The main energy providing components of human uterine fluid are lactate and pyruvate. They have very low concentrations belonging to ppm and ppb levels respectively. The flow procedure of their-determination is designed adopting the Anion Exchange Chromatography method. The concentrating and analytical columns used are AG6 and AS6 respectively. A total of 59 women of child-bearing age with normal menstrual cycles were investigated for lactate and pyruvate concentration in the uterine fluid at different days during the menstrual cycle. Dynamic curves were plotted. The results obtained may give some hints on the appropriate composition of the culture medium used for in vitro fertilization and embryo transfer.

[Effect of a new positive inotropic agent (OPC-8212) on intracellular potential of isolated canine ventricular papillary muscle]

This study adopted intracellular microelectrode technic to observe the effect of OPC-8212 (Vesnarinone) on intracellular potential of isolated canine ventricular papillary muscle. The record and data processing were completed by computerized intellective instrument designed by ourselves. The results of intracellular record in 14 canine ventricular papillary muscle showed no significant change in the resting potential (RP), amplitude of action potential (APA) and maximum depolarize velocity of 0 phase (Vmax). But significantly increased whole duration of action potential (APT). The duration of repolarization to 1/3 (APD 1/3) and to 2/3 (APD 2/3) significantly increased too. The plateau phase raised. These results suggest that K+ permeability at resting myocardiac cell membrane may have not been effected by OPC-8212. Activation of the fast sodium channel may have not been effected too. The results of our studies also suggest that inward flow of Ca2+ increased. The delayed outward K+ (Ik) and the inward, rectifying K+ current (Ik1) possible decreased. Thus, the OPC-8212 might become a nonglucoside and noncatecholamine new positive inotropic drug.

Microvascular vasopressin effects during endotoxin shock in the rat

We have demonstrated decreased microvascular sensitivity to norepinephrine during endotoxin shock possibly related to reduced sympathetic receptor activity (Baker et al.: Circ Shock 12:165-176, 1984). The response to other vascular controls such as arginine vasopressin (AVP) may also be altered. Reactivity of the left cremaster muscle microvessels of pentobarbital anesthetized Wistar rats was studied using videomicroscopy and videodensitometry. Femoral arterial pressure (Pm), dose response curves of vessel diameters to topical arginine vasopressin (10(-15) to 10(-6) M), FITC-albumin mean transit times, and plasma velocities were obtained. Escherichia coli endotoxin (6 mg/kg i.v., LD100) was infused over a 1-hr period. Parameter measurements were repeated at 30 min and 90 min post-endotoxin. Both Pm and plasma velocities progressively decreased. Arteriolar constriction and the mean transit times of FITC-labeled albumin progressively increased. The threshold dose for AVP averaged 10(-9) M at control and decreased to 10(-14) M post-endotoxin. Venular diameters were not altered by AVP. The AVP antagonist did not alter the microvascular diameter response to endotoxin but did block the responses to topical and endogenous AVP since arterial pressure and flow velocity decreased at a significantly greater rate than in rats without antagonist. Plasma AVP levels were significantly increased by endotoxin. Reduced alpha adrenergic sensitivity may unmask the responsiveness to AVP or increase the sensitivity of AVP receptors. Increased endogenous AVP may require a smaller exogenous concentration of AVP for constriction.

Identification and sequence of the drpA gene from Escherichia coli

The drpA gene of Escherichia coli encodes a factor that is involved in global RNA synthesis. We establish that the drpA gene has been successfully cloned and describe the fine-structure map of three drpA-(Ts) mutations as well as the complete nucleotide sequence of the drpA gene. We identified a major sigma-70 promoter for the drpA gene on the bases of (i) its similarity to the consensus sequence and (ii) S1 protection and primer extension mapping data. In addition, the nucleotide sequence revealed a pair of dnaA boxes and a factor-independent terminator at the 5' end and 3' end of the gene, respectively. The deduced amino acid sequence of the DrpA protein showed a nucleotide-binding pocket found in some ATPases.

[Application and mechanism of radix et rhizoma rhei in treating diseases of the digestive system]

Radix et Rhizoma Rhei is a commonly used Chinese medicinal herb with unique function. The present study is concerned with the application and mechanism of the herb in the treatment of diseases of digestive system.

Cellular pharmacology of 3'-azido-3'-deoxythymidine with evidence of incorporation into DNA of human bone marrow cells

We previously demonstrated that 3'-azido-3'-deoxythymidine (AZT) inhibits growth proliferation of human bone marrow progenitor cells in vitro [Antimicrob. Agents Chemother. 31:452-454 (1987)]. The present study evaluates the effect of toxic concentrations of AZT on possible sites of toxicity in human bone marrow cells. Exposure of cells over a 6-hr period to AZT concentrations between 0.5 and 50 microM resulted in a decreased incorporation of tritiated deoxyguanosine into DNA. Unchanged AZT and its phosphorylated metabolites accumulated within cells after exposure to 10 microM [3H]AZT. 3'-Azido-3'-deoxythymidine-5'-monophosphate was the predominant metabolite, reaching a concentration of 49.2 +/- 14.1 pmol/10(6) cells after 48 hr, and a continuous increase was observed in all phosphorylated derivative levels between 2 and 48 hr of incubation. Using a highly sensitive and specific DNA polymerase assay, endogenous deoxyribonucleotide pool size(s) were analyzed for 48 hr after incubation of cells with a pharmacologically relevant concentration of 10 microM AZT. After a 6-hr exposure, 2'-deoxycytidine-5'-triphosphate and 2'-deoxythymidine-5'-triphosphate pools represented approximately 86 and 70% of the control values; levels returned to normal after 24 hr and remained subsequently unchanged. Nucleic acids of human bone marrow cells exposed for 24 hr to 10 microM [3H]AZT were purified and analyzed by cesium sulfate density gradient. No radioactivity was detected in the RNA region, whereas a significant amount was associated with the DNA region. Hydrolysis of radiolabeled DNA and subsequent analysis by high performance liquid chromatography demonstrated specific incorporation of AZT into DNA. In additional studies, the amount of AZT incorporated into DNA was correlated with the initial extracellular AZT concentration. In particular, a significant relationship (p less than 0.0001) between the level of AZT incorporated into DNA and the inhibition of clonal growth was observed at concentrations of AZT between 1 and 25 microM (IC50 and IC85 for human bone marrow cells). In summary, these studies demonstrate that AZT is incorporated into DNA of human bone marrow cells and suggest that incorporation of AZT into DNA may be one mechanism responsible for AZT-induced bone marrow toxicity. In contrast, imbalance of deoxyribonucleotide pools by AZT appears unlikely to be associated with inhibition of DNA synthesis and toxicity in human bone marrow cells.

Splice variants of the alpha subunit of the G protein Gs activate both adenylyl cyclase and calcium channels

Signal transducing guanine nucleotide binding (G) proteins are heterotrimers with different alpha subunits that confer specificity for interactions with receptors and effectors. Eight to ten such G proteins couple a large number of receptors for hormones and neurotransmitters to at least eight different effectors. Although one G protein can interact with several receptors, a given G protein was thought to interact with but one effector. The recent finding that voltage-gated calcium channels are stimulated by purified Gs, which stimulates adenylyl cyclase, challenged this concept. However, purified Gs may have four distinct alpha-subunit polypeptides, produced by alternative splicing of messenger RNA. By using recombinant DNA techniques, three of the splice variants were synthesized in Escherichia coli and each variant was shown to stimulate both adenylyl cyclase and calcium channels. Thus, a single G protein alpha subunit may regulate more than one effector function.

[Studies on the introduction and cultivation of Kaempferia galanga L]

This paper reports a systematic survey of the biological character istics of K. galanga. As a result of investigations on plant density, planting season, fertilization, storage of maternal tubers in winter and qualitative analysis of tubers, etc, cultural measures have been brought forth that suit the local climatic conditions and thus give high yield and quality of products.

Uridine reverses the toxicity of 3'-azido-3'-deoxythymidine in normal human granulocyte-macrophage progenitor cells in vitro without impairment of antiretroviral activity

We evaluated the effects of natural purine and pyrimidine nucleosides on protection from or reversal of 3'-azido-3'-deoxythymidine (AZT) cytotoxicity in human bone marrow progenitor cells by using clonogenic assays. The selectivity of the "protection" or "rescue" agents was examined in evaluating the antiretroviral activity of AZT in combination with these modulating agents and of AZT alone. Following exposure of human granulocyte-macrophage progenitor cells for 2 h to 5 microM AZT (70% inhibitory concentration), increasing concentrations of potential rescue agents were added. Cells were cultured, and colony formation was assessed after 14 days. At concentrations of up to 50 microM no natural 2'-deoxynucleosides, including thymidine, were able to reverse the toxic effects of AZT. Dose-dependent reversal was observed with uridine and cytidine, and essentially complete reversal was achieved with 50 microM uridine. In the protection studies, 100 microM thymidine almost completely antagonized the inhibition of granulocyte-macrophage colony formation produced by 1 microM AZT (50% inhibitory concentration), and 50 microM uridine effected 60% protection against a toxic concentration of AZT (5 microM) (70% inhibitory concentration). The antiretroviral activity of AZT in human peripheral blood mononuclear cells, assessed by revere transcriptase assays, was substantially decreased in the presence of thymidine, whereas no impairment of suppression of viral replication was observed in the presence of uridine in combination with AZT at a molar ratio (uridine/AZT) as high as 10,000. This demonstration of the capacity of uridine to selectively rescue human bone marrow progenitor cells from the cytotoxicity of AZT suggests that use of uridine rescue regimen with AZT may have potential therapeutic benefit in the treatment of acquired immunodeficiency syndrome.

Optimization of information pit shape and read-out system in read-only and write-once optical storage systems

The 3-D diffraction behavior of an optical recording is investigated using the rigorous mode approach. Relationships between desirable pit shapes, write-in conditions, and read-out characteristics are discussed.

Expression of single calcium channels in Xenopus oocytes after injection of mRNA from rat heart

Oocytes of Xenopus laevis, after microinjection with mRNA from rat heart, display typical high-threshold calcium (Ca) whole cell currents. To prepare to study structure-function relationships of the cardiac Ca channel molecule, we examined the fidelity of expression of biophysical and pharmacological properties at the molecular level. Cell-attached gigaseal recordings in five K-depolarized oocytes injected with adult rat heart mRNA showed single channel Ba currents with mean amplitude 1.3-1.5 pA at 0 mV, slope conductance 18-25 pS, and extrapolated reversal potential 57-68 mV. Openings were predominantly brief (mean 1.2 ms) but longer openings (mean 9 ms) were greatly enhanced in 10(-6) M BAY-K 8644, increasing the ensemble average current at 0 mV by more than fivefold. These features are typical of high-threshold cardiac Ca channels. In two patches from one injected oocyte, we saw multiple Ca channel conductances, as recently observed in other preparations. We conclude that X. laevis oocytes injected with adult rat heart mRNA produce high-threshold cardiac Ca channels with molecular properties identical to native cells.

Expression of single calcium channels in Xenopus oocytes after injection of mRNA from rat heart

Page H985: J. R. Moorman, Z. Zhou, G. E. Kirsch, A. E. Lacerda, J. M. Caffrey, D. M.-K. Lam, R. H. Joho, and A. M. Brown. “Expression of single calcium channels in Xenopus oocytes after injection of mRNA from rat heart.” Page H991: the following should have been included in the acknowledgements: We are grateful to John Leonard and Terry Snutch for their help and advice with the oocyte expression system.

Efficacy of vaccination with Skinner vaccine towards the prevention of herpes simplex virus induced cervical carcinoma in an experimental mouse model

The incidence of cervical carcinoma, which had been induced by vaginal application of inactivated herpes simplex virus type 2 (HSV-2) with 20% croton oil, was significantly reduced in mice prevaccinated with the Skinner herpes vaccine. There was evidence of an immunological response in both vaccinated and unvaccinated mice.